Screw cap



Oct. 15, 1963 J. w. WANDELL SCREW CAP 4 Sheets-Sheet 1 Original Filed Jan. 13, 1958 INVEN TOR Jiwu li flA/ozu Oct. 15, 1963 J. w. WANDELL 3,107,022

SCREW CAP Original Filed Jan. 13, 1958/ 4 Sheets-Sheet 2 v :A 5 a INVENTOR Jab/Es lZ/ZM/ZMZL 'Oct. 15, 1963 J. w. WANDELL SCREW CAP 4 Sheets-Sheet s Original Filed Jan. 15, 1958 Ill/flit f, A w

T1 21-5. Tlc'li. T l 3-11.

Oct. 15, 1963 J. w. WANDELL 3,107,022

SCREW CAP Original Filed Jan. 13, 1958 4 Sheets-Sheet 4 INVENTOR $0455 M h/woezz United States Patent Oiifice arenas Patented Get. 15, 1963 3,lfi7,tl22 SEREW (IA? ames W. Wendell, 1591 Metropolitan Ave, Bronx, N32. Continuation of application Ser. No. 708,596, Jan. 13, 1958. This application Early 10, B62, Ser. No. 219,391

2 iliaims. (Sl. 215- 23) This invention relates to a screw cap for bottles, cans and similar containers, and more specifically relates to an improved plastic screw cap which does not require a liner to form a liquid-tight seal when positioned over the mouth of a bottle, can, or similar container.

It is commonly known and understood that the screw caps now being used for the purpose of closing a container such as a bottle or can, require a liner inside the cap in order that a liquid-tight seal be provided by the top of the bottle or can neck and the inside of the cap. It has been customary to utilize cap liners consisting of materials such as laminated cardboard, cork, metal foil and the like. The insertion of the liners into the domes of screw caps by the customary methods requires the use of expensive equipment and additional labor costs.

One of the objects of the present invention is to provide an improved screw cap of the character indicated which eliminates the necessity for a liner and provides a liquidtight seal when the cap is positioned over the neck of the container such as a bottle or can.

It is another object of this invention to provide an improved one-piece, plastic screw cap which has the ability of being tightly seated on the neck of the container, such as a bottle or can, to provide a liquid-tight seal.

O her objects and advantages of tits invention will be apparent from the following description when taken in connection with the drawing in which similar characters of references indicate similar parts throughout the several views.

Referring to the drawings:

FIGURE 1 is a view in section of one form of the cap and a fragmentary view of a bottle showing a portion of the bottle neck in section;

FIGURE 2 is a view in section of the cap of FIGURE 1 and a bottle neck showing the cap incompletely seated on the bottle neck;

FIGURE 3 is a view similar to the view of FIGURE 2 showin the cap fully seated on the bottle neck;

FIGURE 4 is a view in section of another form of the cap and a fragmentary view of a bottle showing a portion of the bottle neck in section;

FIGURE 5 is a view in section or" the cap of FIGURE 4 and a bottle neck showing the cap incompletely seated on the bcttie neck;

FlGURE 6 is a view similar to the view of FIGURE 5 showing the cap of FIGURE 4 fully seated on the bottle neck;

FIGURE 7 is a fragmentary view in section of a pen tion of the skirt of a modified form of the cap showing a stabilizing ring;

FIGURE 8 is a view in section of the cap of FIGURE 7 and a bottle neck showing the cap fully seated on the bottle neck;

FIGURES 9, l0 and 11 are fragmentary views in section showing three structural modifications of the side wall of the cap;

FIGURE 12 is a view in section of still another form of the cap and a fragmentary view of a bottle showing a portion of the bottle neck in section;

FIGURE 13 is a View in section of the cap of FIGURE 12 and a botne neck showing the cap incompletely seated on the bottle neck;

FIGURE 14 is a view similar to the view of FIGURE 13 showing the cap fully seated on the bottle neck;

FIGURE 15 is an enlarged fragmentary view in section of a portion of the cap of FIGURE 12 and a bottle neck showing the cap incompletely seated on the bottle neck; and

FTGURE 16 is an enlar ed fragmentary view in section of a portion of the cap of FIGURE 12 and a bottle neck showing the cap fully seated on the bottle neck.

Referring to the drawing and particularly to FIGURE 1, the cap, which is indicated generally at 1, has a side wall 3, an inner surface of the side wall 4, an internal ring 5 integrally formed with and protruding from the inner surface of the top of the cap a distance substantially less than the internal depth of the cap, threads 7 and an end wall Internal ring 5 has a frusto-conical outer surface 15 which is inclined inwardly from its base and uniformily around its circumference. The base of the ring 13 is positioned away from the inner wall of the cap so that there is an inner surface of the cap 11 between the base of the ring and the inner surface of the side wall of the cap. The inner surface 17 of the ring of FIGURE 1 is substantially parallel with the inner wall of the cap. The outer surface of the rin is preferably at an angle with respect to the inner wall of the ring such that the base of the ring is substantially thicker than the tip of the ring. It is contemplated that in another modification of the cap, the ring may have the shape of a n'gh -angle triangle with the base thereof formed integrally with the inner surface of the cap top and with the hypotenuse thereof facing the inner cap wall. The preferred form of internal ring 5 is illustrated in FIGURES 4, 5 and 6 which show an internal ring 5 having an inner surface 17 positioned at an angle with respect to the surface 9 within the ring of less than and an outer surface 15 inclined inwardly and uniformly substantially around its circumference and positioned at an angle with respect to the surface 9 within the ring less than the angle at which inner surface 17 is positioned with respect thereto. The ring in this modification protrudes from the inner surface of the cap a distance substantially less than the internal depth of the cap. It is preferred that the inner and outer surfaces of the ring be positioned at angles of about 60 and 45, respectively, with respect to the cap surface 9 within the ring. This provides an internal ring which is thicker at the base than the tip and is undercut with respect to the interior of the ring. The ring having the configuration illustrated in FIGURES 4, 5 and 6, has greater flexibility than the ring illustrated in FIGURES l, 2 and 3 because it is thinner and therefore provides a better seal with the bottle neck by conforming more closely with any irregularities of the inner edge 2? of the top 25 of the bottle neck to which the external surface 15 of the ring comes in contact. A relatively thinner ring with an undercut conformation also requires less pressure of the ring on the internal edge of the bottle neck to form a liquid-tight seal and thereby reduces any tendency for the bottle neck to crack.

FIGURE 7 shows a cap having a stabilizing ring 4 protruding from the inner surface of the cap wall 3 below the threads 7. The stabilizing ring is adapted to come in contact with and seat on head 2%) at the base of the bottle neck when the cap is fully seated. FIGURE 8 shows the stabilizing ring seated on the bead and the cap fully seated on the bottle neck. Most conventional bottles have a head at the base of the neck to lessen the tendency of conventional screw caps to cock. The stabilizing ring acts as an additional safeguard to prevent the cap from cocking and also from stripping over the threads when relatively extreme pressure is applied by rotation of the cap as may occasionally happen when bottles are capped by means of the automatic bottle capping machinery conventionally employed in the industry. In the preferred form of the stabilizing ring, as particularly illustrated in 3 FIGURE 7, the bottom surface 2 of the stabilizing ring forms a right angle with the inner surface 4 of the cap wall.

The external wall 3a, 3b and 3c of the three separate modifications of the cap illustrated in FIGURES 9, l and 11, respectively, has an area of greater lateral flexibility at a point between the beginning and ending of the threads on the internal surface of the cap. In all three of the modifications of FIGURES 9, 10 and 11 the side wall of the cap is slightly thinner at a point about onethird the length of the cap wall from the top of the cap. The external cap Wall is tapered inwardly from the top at an angle within the range of from about 0.5 to 2, about 0.5 being preferred and the inwardly tapered portion extends down about one-third the length of the cap. From approximately the point Where the inwardly tapered portion ends, the cap wall is tapered outwardly to the end at an angle within the range of from about 05 to 2, about 1 being preferred. In the preferred form of the cap having a wall with an area of greater lateral flexibility, as illustrated in FIGURE 9, the external wall 3a is parallel with the internal Wall for a short distance between the end of the inwardly tapered portion and the beginning of the outwardly tapered portion. FIGURE illustrates a form of the cap in which the external wall 3b is slightly rounded at the point Where the inwardly tapered portion ends and the outwardly tapered portion begins. FIGURE 11 illustrates a form of the cap in which the outwardly tapered portion of the exterior cap wall, 3c begins at the point where the inwardly tapered portion ends. In all three modifications of the outer form of the cap Wall illustrated in FIGURES 9, l0 and 11, the area of greater lateral flexibility of the cap Wall is positioned below the top of the thread nearest the inner end surface of the cap.

A plastic cap having an area of greater lateral flexibility of the side wall has less tendency to strip over the threads of the bottle when relatively great force is applied by rotation of the cap during a capping operation in which conventional capping machinery is used. When such conditions of relatively great force occur, the threads of a cap having a side wall with an area of greater lateral flexibility, as illustrated in FIGURES 9, 10 and 11, have a substantially reduced tendency to strip over the threads of the bottle because the cap wall yields and bulges outwardly slightly at the area of greater lateral flexibility and thus relieves the pressure of the end of the bottle neck on the interior surface of the cap.

The cap illustrated in FIGURES 12 to 16 inclusive has a small internal ring 31 integrally formed with and protruding from the inner surface of the cap end 11 between the outer surface 15 of ring 5 and the inner surface 4 of the cap wall. The small ring 31 may have substantially the same shape as the inner rings 5, as illustrated in FIGURES l and 4, that is, with a base substantially thicker than the tip, such as a ring having the shape in cross-section of an equilateral triangle. It is preferred that the small ring 31 be undercut, have an inner surface positioned at an angle with respect to the surface Within the ring of less than 90 and an outer surface positioned at an angle with respect to the surface within the ring less than the angle at which the inner surface of the ring is positioned thereto, as illustrated in FIGURES 12 to 16 inclusive. When a cap having the small undercut ring of FIGURES 12 to 16 inclusive is fully seated on the bottle neck the end 27 of the bottle neck compresses the small ring by bending it slightly in the direction of inner ring 5. It frequently happens that the end 27 of a bottle neck is not flat but has minor surface irregularities which make a fluid-tight closure difficult to attain. The small ring provides an additional safeguard against leakage of a liquid from a bottle having minor surface irregularities on the end 27 of the neck and particularly leakage of a liquid such as an aqueous alcoholic solution which has a relatively low surface tension.

As a cap, such as is illustrated in the drawings, is positioned over the neck 21 of the bottle 1?, the threads 7 on the internal surface of the cap engage with the threads 23 on the outer surface of the neck of the bottle. As the cap is rotated about the neck of the bottle, the inner edge 29 of the top 25 of the bottle neck 21, which is slightly rounded or beveled, comes in contact with the outer surface 15 of the ring and at this point the cap is not yet fully seated on the container neck. The cap is shown in FIGURES 2, 5, 13 and 15, with the inner edge 22 of the container neck making initial contact with the outer surface 15 of the ring. As the cap is given additional rotation, the inner edge 29 of the bottle neck compresses inner ring 5 of the cap inwardly and slides along the outer surface 15 of the ring to the base 13 of the ring and approximately at this degree of rotation of the cap about the bottle neck, the top surface 27 of the container neck 25 seats firmly against the inner surface 11 of the cap which is between the inner side wall 4 of the cap and the base 13 of the inner ring 5. The cap is shown in FIGURES 3 and 6 after additional rotation has been given over the rotation in FIGURES 2 and 5, with the inner edge 29 of the top 25 of the container neck in contact with the base 13 of the outer surface 15 of the ring and with the top surface 27 of the container neck in contact with and firmly seated against the inner end Wall 11 of the cap. When the cap is firmly seated on the container neck, a liquid-tight seal is formed.

As the inner edge 29 of the bottle neck comes in contact with the outer surface 15 of the ring of the cap of FIGURES 12 to 16 inclusive, the end surface 27 of the bottle neck simultaneously comes in contact with the small ring 31, as shown in FIGURES 13 and 15, and when the cap is given additional rotation, the ring 5 is compressed slightly and the inner edge 29 of the bottle neck compresses the inner ring 5 of the cap inwardly and slides along the outer surface 15 of the ring toward the base 13 thereof and the small ring is compressed as illustrated in FIGURES l4 and 16.

Although all of the figures of the drawings and the description above illustrate the screw cap of my invention as adapted for use as a closure for a bottle. It is to be understood that the screw caps of my invention are not limited to use as a closure for bottles but are suitable for use as closures with any container, such as a metal can or plastic container, with which a screw cap closure may be employed.

In general, any synthetic plastic material having a relatively low elasticity and a relatively high stiffness is suitable for use in fabricating the screw caps of my invention. Such materials include but are not limited to polymers of ethylene, polymers of propylene, and copolymers of ethylene and propylene. It is preferred that the synthetic plastic materials have a stiffness within the range of from about 50,000l50,000 pounds per square inch, as determined according to ASTM test method D747-50. Long-chain high density polyethylenes having mainly terminal vinyl groups, essentially no trans structure, essentially no branched vinyl groups, a relatively high degree of crystallinity, a relatively large molecular Weight, and a relatively high density, softening temperature and tensile strength are generally preferred for use in fabricating the screw caps of my invention. Still more particularly, the preferred materials for use in fabricating the screw caps of my invention are long-chain polyethylenes having mainly terminal vinyl groups, essentially no branched vinyl groups, essentially no trans structure, a crystallinity of at least about 93 percent, a density of about 0.95 to 0.97 gram per cubic centimeter, a softening temperature of about 230 F. to 260 F., and a stiffness within the range of from about 50,000 to 150,000 pounds per square inch, as determined. by ASTM test method D747-50.

The screw cap of this invention may be fabricated by the use of conventional injection moulding equipment and, because of the above-defined physical characteristics of the plastic substance, may be ejected from the mould without mutilation of the internal threads of the cap.

Although the construction of the screw cap of this invention has been described in some detail, it is to be understood that the description is solely to illustrate concrete and preferred embodiments thereof and that the invention is not to be limited to the exact description and drawings except as such limitations may appear in the appended claims.

This application is a continuation of my application Serial No. 708,596, filed January 13, 1958, which is in turn a :continuation-in-part of my application Serial No. 645,705, filed March 13, 1957, both abandoned.

I claim:

'1. In combination with a container having an exteriorly threaded neck with a mouth therethrough, a unitary, internally threaded cap consisting essentially of a synthetic plastic material having a stiffness within the range from about 50,000 to 150,000 pounds per square inch and adapted to fit over said neck and close said mouth, the cap having a side wall, a top wall comprising an annular wall portion extending inwardly from the side Wall, said annular wall portion having a lower annular surface portion, and an internal sealing ring integrally formed with and protruding from the inner surface of the top wall at the inner portion of the annular wall portion thereof, said ring protruding from said inner surface a distance which is a minor fraction of the internal depth of the cap and being relatively more flexible than said annular wall portion, said ring being thinner throughout its height than said annular wall portion, said ring having downwardly converging frustro-conical inner and outer surfaces, said ring and lower annular surface portion having a size and configuration relative to the size and configuration of the neck of the container so that, as the cap is positioned on the neck of the container by rotation and the threads of the cap engage with the threads of the container, the container neck is in contact at its top inner edge with the outer surface of the ring before the cap is fully seated and when the cap is fully seated the ring is slightly compressed, the top inner edge of the container neck is seated firmly against the base portion of the ring, and the top of the neck is seated firmly against said lower annular surface portion.

2. In combination with a container having an exteriorly threaded neck with a mouth therethrough, a unitary, internally threaded cap consisting essentially of a synthetic plastic material having a stiffness within the range from about 50,000 to 150,000 pounds per square inch and adapted to fit over said neck and close said mouth, the cap having a top wall, a side wall having a downwardly extending internal surface with a threaded section in which threads extend inwardly from said surface, said side wall being tapered on the exterior inwardly from the top thereof to converge toward said internal surface to a point abreast said threaded section and tapered outwardly to diverge from said internal surface from approximately the point where the inwardly tapered portion ends to the end of the cap wall, whereb the side wall of the cap is slightly thinner outside said threads and has an area of greater lateral flexibility at a point between the beginning and ending of said threads, said top wall having an annular wall portion extending inwardly from the side wall, said annular wall portion having a lower annular surface portion, and an internal sealing ring integrally formed with and prot-Fllding downwardly from the inner surface of said top wall at the inner portion of the annular wall portion thereof, said ring protruding from said inner surface a distance which is a minor fraction of the internal depth of the cap and being relatively more flexible than said annular wall portion, the ring being thinner throughout its height than said annular wall portion, said ring having downwardly converging frustro-conical inner and outer surfaces, said cap having a size and configuration relative to the size and configuration of the neck of the container so that, as the cap is positioned on the neck of the container by rotation and the threads of the cap engage with the threads of the container, the container neck is in contact at its top inner edge with the outer surface of the ring before the cap is fully seated and when the cap is fully seated the ring is slightly compressed, the top inner edge of the container neck is seated firmly against the base portion of the ring, and the top of the neck is seated firmly against said lower annular surface portion, and so that the application of additional force by rotation of the cap after it is fully seated causes the cap side wall to yield and bulge outwardly slightly at said area of greater lateral flexibility, whereby the pressure of the end of the container neck on said lower annular surface portion is relieved.

References Cited in the file of this patent UNITED STATES PATENTS 2,582,721 Roshkind Jan. 15, 1952 2,684,168 McGinnis et a1. July 20, 1954 FOREIGN PATENTS 810,349 Germany Aug. 9, 1951 1,050,249 France Oct. 26, 1953 782,574 Great Britain Sept. 11, 1957 788,148 Great Britain Dec. 23, 1957 1,230,375 France July 20, 1959 

1. IN COMBINATION WITH A CONTAINER HAVING AN EXTERIORLY THREADED NECK WITH A MOUTH THERETHROUGH, A UNITARY, INTERNALLY THREADED CAP CONSISTING ESSENTIALLY OF A SYNTHETIC PLASTIC MATERIAL HAVING A STIFFNESS WITH THE RANGE FROM ABOUT 50,000 TO 150,000 POUNDS PER SQUARE INCH AND ADAPTED TO FIT OVER SAID NECK AND CLOSE SAID MOUTH, THE CAP HAVING A SIDE WALL, A TOP WALL COMPRISING AN ANNULAR WALL PORTION EXTENDING INWARDLY FROM THE SIDE WALL, SAID ANNULAR WALL PORTION HAVING A LOWER ANNULAR SURFACE PORTION, AND AN INTERNAL SEALING RING INTEGRALLY FORMED WITH AND PROTRUDING FROM THE INNER SURFACE OF THE TOP WALL AT THE INNER PORTION OF THE ANNULAR WALL PORTION THEREOF, SAID RING PROTRUDING FROM SAID INNER SURFACE A DISTANCE WHICH IS A MINOR FRACTION OF THE INTERNAL DEPTH OF THE CAP AND BEING RELATIVELY MORE FLEXIBLE THAN SAID ANNULAR WALL PORTION, SAID RING BEING THINNER THROUGHOUT ITS HEIGHT THAN SAID ANNULAR WALL PORTION, SAID RING HAVING DOWNWARDLY CONVERGING FRUSTRO-CONICAL INNER AND OUTER SURFACES, SAID RING LOWER ANNULAR SURFACE PORTION HAVING A SIZE AND CONFIGURATION RELATIVE TO THE SIZE AND CONFIGURATION OF THE NECK OF THE CONTAINER SO THAT, AS THE CAP IS POSITIONED ON THE NECK OF THE CONTAINER BY ROTATION AND THE THREADS OF THE CAP ENGAGE WITH THE THREADS OF THE CONTAINER, THE CONTAINER NECK IS IN CONTACT AT ITS TOP INNER EDGE WITH THE OUTER SURFACE OF THE RING BEFORE THE CAP IS FULLY SEATED AND WHEN THE CAP IS FULLY SEATED THE RING IS SLIGHTLY COMPRESSED, THE TOP INNER EDGE OF THE CONTAINER NECK IS SEATED FIRMLY AGAINST THE BASE PORTION OF THE RING, AND THE TOP OF THE NECK IS SEATED FIRMLY AGAINST SAID LOWER ANNULAR SURFACE PORTION. 